I wonder how much of these numbers with Catholics is due to lapsing/secularization/movement to mainline Protestantism or not-particularly-conservative Evangelicalism among whites and how much is due to Evangelical and Pentecostal conversion efforts among Hispanics. I'm not trying to imply anything by saying that, I'm genuinely curious.
I also think people are understating how important to a successful marriage they think shared politics is, considering that other studies (I'm afraid I can't cite them off the top of my head) have shown that political mixed marriages are actually becoming less common than religious mixed marriages these days.
I wonder how much of this is just due to increased ideological sorting of the parties, though? Someone who held socially liberal "cosmopolitan" views in the 1960's probably would be unlikely to marry someone who was reactionary/conservative for their day, even if they were both in the same party. Today, there's a lot more homogeneity in beliefs amongst the two parties, so it seems like the signal of ideology's effect on marriage is just being picked up more strongly than it did in the past because the parties are more ideologically coherent.
